To begin understanding the relationship between sleep and mood, it’s helpful to think about babies! When discovering more about our own mood in relation to sleep, it can be interesting to learn about how we acted as a sleepy child. Try calling up your parents and ask them, as a baby, how did I act when I was tired? It is likely they will mention something in relation to mood. Perhaps their clue that you needed a nap was when you became cranky, cried, or angrily threw your toys around. Babies are a great, unfiltered example of how being tired affects our mood. When we get older, many of us think we outgrow the childish behavior of getting upset when we are tired. However, throughout the course of this module, it should become clear that sleeping patterns continue to strongly influence our mood, even as adults.
It is known that during sleep, your body produces various hormones that affect your appetite, weight and immune system. Now sleep studies are linking these effects to mood, showing that partial sleep deprivation has a significant effect on perceived happiness. University of Pennsylvania researchers found that subjects who were limited to only 4.5 hours of sleep a night for one week reported feeling more stressed, angry, sad, and mentally exhausted (GetSleep). When these subjects were asked to resume normal sleep, they reported a dramatic improvement in mood (GetSleep).
College can be a stressful time for multiple reasons; whether it’s juggling work, school, relationships, or living away from home, perhaps you have personally felt an uncomfortable shift in mood during times of high stress and reduced sleep.
But how is sleep so tightly interconnected with one’s mood? As an evolved species, why are we not able to overcome an all nighter with Yerba Mate and sheer will power? Researchers Barber & Munz hypothesize that it might have something to do with self control. In social psychology, there is a prevalent theory called the self-regulatory strength model. This model postulates that we all have a limited amount of self control that lessens every time we do an activity that is taxing either emotionally, physically, or mentally. Think of this like running timed laps. The more laps you run, the more you deplete stored energy resources. According to this theory, self control works the same way! Thus, the more self control we exert, the less mental resources we will have to control certain impulses, such as our initial emotional responses to our environment.
Barber & Munz argue that sleeping sufficiently as well as maintaining a consistent wake up and bedtime can help replenish and increase our self-regulatory resources, potentially affecting our mood!
They tested this hypothesis by measuring a group of undergraduate students’ sleeping patterns as well as their psychological strain throughout the week. Psychological strain was measured as a type of stress exemplifying the feeling of not having the sufficient internal resources to meet an external demand: an example of potential insufficient self-regulatory resources. Barber & Munz found that students who were consistent and adequate sleepers were the only group that saw a decrease in psychological strain throughout the work week. Thus, it seems that getting enough sleep and replenishing one’s internal resources can help lead to less perceived stress and psychological strain in one’s day to day life.
A study by Chue et al. (2018) also supports the finding that sleep significantly impacts how much individuals are affected by stress. Specifically, this study looked at whether a good night’s sleep can help decrease the negative mood spillover from a previously stressful day and help us bounce back to normal. The researchers found that getting enough sleep after a highly stressful day decreased the negative affect (the personal experience of negative emotional states) individuals felt the next morning. On the other hand, increased sleep debt (measured in this study as the number of days participants slept less than 6 hours) led to increased negative affect the morning following a stressful day. These findings point to how important good, consistent sleep is to decreasing the negative emotional spillover from a stressful day.
What about positive emotion? Sleep can affect that too! Increased sleep time and decreased sleep debt corresponded with a greater positive affect for participants following a high stress day. In fact, the positive effect after better sleep was increased to the same levels that those with a previously low stress day felt in the morning! It is natural to have some amount of stress in our lives, especially with all the pressures students undergo at a top research University. Remember that sleep can not only help decrease a negative emotional spillover from one stressful day to the next (aka finals!), it can also help you positively bounce back to your normal baseline mood after a particularly stressful day.
Sleep’s effect on mood can have a big impact on other parts of our lives, such as performance in school. The following correlational study focused on adolescents from 13-18 and found, consistent with our module thus far, that poorer sleep quality leads to a more depressive mood. Additionally, these researchers also found a critical correlation in the relationship between sleep, mood, and academic performance!
In this study, students who reported more daytime sleepiness were more likely to have reduced academic performance. Researchers found that this relationship was indirect and actually mediated by daytime sleepiness’ association with a worse mood. In other words, students performed worse in school not necessarily because they were sleepier, but because their sleepiness was associated with a worse mood. Thus, this study supports the relationship between sleepiness and mood, and emphasizes how this relationship can affect our lives, especially as college students!
So far, we’ve learned that poor sleep quality may impact our daily moods more so than initially thought. Is this relationship the same for those who have mood disorders such as anxiety and depression? The following study conducted daily assessments of sleep quality and mood for 6 weeks for different groups of participants. Participants were sorted into four diagnosed groups:
- Anxiety and depression
- Neither anxiety nor depression
(participants were screened with the Patient Health Questionnaire Anxiety-Depression Scale as a composite measure of depression and anxiety)
Ultimately, researchers found that mood most affected sleep quality in participants with anxiety. These results suggest that in the case of those with high anxiety, implementing relaxation techniques may help to improve sleep. However, the sleep quality of participants with neither anxiety nor depression (the control group) had the biggest effect on their mood the following day. This evidence indicates that prioritizing sleep can benefit mood the next morning for those without depression or anxiety.
If we dive a little deeper, it seems that the lack of correlation between sleep quality and mood for those with mood disorders may be significant when looking at negative affect, but not positive affect. In a correlational study, researchers asked people with major depressive disorder, minor depressive disorder, and no mood disorder to report their positive or negative affect 10 times a day for three days along with an extensive measure of their sleep quality in the past month. After accounting for differences in depression and anxiety, sleep quality was still a significant predictor of the variance in participants’ daily positive affect. On the other hand, after accounting for differences in depression, sleep quality was no longer a significant predictor of the variance in participants’ daily negative affect. From this information, we can infer that for individuals with depression, adequate sleep may contribute to the experience of positive emotions the following day. Although mood disorders can complicate one’s relationship with sleep, getting a good night’s sleep is still an important factor for daily mood!
Although your mood might not be the first thing that comes to mind when reflecting on sleep, evidence shows that one should take this relationship into consideration. We may not be able to control external stressors throughout our day, but there are many things we can do to help improve our state of mind, including getting a good night's sleep!